Factors affecting the free fatty acids in rat brain cortex

The mode of free fatty acid (FFA) release from rat brain cortex was examined under various treatments prior to decapitation and at various times after decapitation. Brain FFA are comprised mainly of 16:0, 18:0, 18:1 and 20:4 with smaller amounts of 18:2, 22:4 and 22:6. A biphasic mode of FFA release is observed with respect to post-decapitative ischemic treatment. The initial rapid phase involves a 3-fold increase in 18:0 and 20:4 and this process occurs within the first min of decapitation. The second phase involves a less rapid increase of most fatty acids between 2 and 5 min after decapitation. Besides the ischemia-induced increase in brain FFA, the levels of individual fatty acids are also affected by factors such as handling stress and administration of anesthetic agents. Pentobarbital anesthesia, but not ketamine, caused a partial reduction in 18:0 and 20:4 levels in brain in vivo. Pentobarbital treatment also reduced the rapid phase of FFA increase commencing after decapitation. On the other hand, FFA level was higher in animals subjected to ketamine anesthesia, both during the non-ischemic and ischemic phase. Results obtained from this study indicate that the FFA pool in brain is regulated by a complex mechanism contributed by extrinsic and intrinsic factors.